Apparatus and method for inserting data effects into a digital data stream

ABSTRACT

The method includes receiving a signal to insert a data effect into a digitally encoded, framed data stream, retrieving a data effect having the same format as that of the data stream, detecting a first data stream frame boundary, inserting the data effect into the data stream at the first data stream frame boundary, detecting a second data stream frame boundary, and resuming the data stream at the second data stream frame boundary. If the data stream can be of more than one format, the format of the data stream can first be determined. The apparatus includes a processor and a multiplexor. The multiplexor is used for inserting the data effect into the data stream. The processor is used for detecting data stream frame boundaries, retrieving from a memory a data effect having the format of the data stream, and transmitting the formatted data effect to the multiplexor. The data stream may be an audio stream formatted in MPEG format (including MPEG-1, MPEG-2, MP3, MPEG-4), AC-3 format (including 2-channel, 5.1-channel, and 7.1-channel), or DTS format. The data effects may be stored in a plurality of formats. Synchronization between the video and audio streams is maintained by dropping frames that are replaced by the data effect. Another method generates a video signal by retrieving a video effect corresponding to an audio effect, inserting the video effect into a video stream associated with an audio stream, and resuming the video stream and audio stream.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of digital audio, video,and multimedia. More specifically, this invention relates to insertingaudio or video effects into a digital audio or video stream.

Digitally-formatted audio (“digital audio”) is becoming more popularbecause of its high quality, its use with computers and compact audioplayers, its ease of manipulation and duplication, and its ability to beshared by many people. Some digital audio formats include uncompressedformats such as Audio Compact Disc (PCM (pulse-code modulation)16-bit/44.1 kHz) and Wave (name extension WAV (.wav)), and compressedformats such as MPEG (Moving Pictures Expert Group) layers 1, 2, 3(MP3), MPEG-4, DTS® (Digital Theater Systems), and Dolby® Digital.

For many of the same reasons, movies and other video broadcasts are alsoincreasingly being transmitted digitally. Thus, a digitally-formattedmovie that is shown in a cinema or delivered to a user's television setfrom a broadcaster (such as a cable broadcaster) will include a digitalvideo stream for the pictures and a digital audio stream for thesoundtrack. One digital audio format used in movies is AC-3, whichencodes multichannel audio. (Dolby® Digital audio is in Dolby® AC-3format.) AC-3 is a compressed format (using perceptual coding) and canbe broadcast in two-channel stereo, “5.1”-channel, or “7.1”-channelformats. The latter two formats are used in surround sound (e.g., Dolby®Surround Digital or Dolby® Surround AC-3). The 5.1-channel formatincludes left front, right front, and center front channels, left andright surround sound channels, and a low frequency effects channel (the“0.1”) having one-tenth the bandwidth of the other channels. The7.1-channel format is analogous to the 5.1-channel format, but includestwo more main channels.

As television becomes more advanced, other applications can beintegrated into the viewing experience. Innovations such as WebTV®,online shopping, electronic program guides, and TiVo® (personal videorecorders) allow the television to be used for more than just watchingTV. While a movie or song is being broadcast, it may be desirable tosend an audible signal to the viewer or listener. One example of such asignal could be an alert from an application such as the America Online(“AOL”) client that the viewer, if watching a movie on a hometelevision, has received a new e-mail message. Other examples include afeedback sound (as part of the user interface) that alerts the user ofthe acceptance of some request (such as by using a remote control), orother sound effects or sound bites that may be used to signal the vieweror listener.

Conventionally, during an audio (analog or digital) broadcast, such asound effect could be broadcast to the user directly, by mixing thesound effect with the soundtrack (primary stream). However, such mixinghas several drawbacks. First, mixing of an analog or uncompresseddigital sound effect requires mixing components, and mixing of acompressed digital sound effect destined for subsequent decodingrequires decompressing (decoding) both the sound effect and the primarystream, mixing the uncompressed signals together, and recompressing(re-encoding) the mixed signal prior to its transmission to the targetdecoder. This can result in poor sound quality and/or a loss ofsynchronization between the audio and video. Second, where a set-top box(“STB”) is used to receive programming, decoding advanced digital audioformats such as AC-3 is usually left to dedicated equipment (e.g., hometheater equipment) external to the set-top box. Some means is thereforerequired for transporting to the external equipment the digital audiodata for both the primary stream and the sound effect, adding cost andcomplexity to the set-up.

Other methods for adding data to a data stream have been disclosed. Forinstance, U.S. Pat. No. 6,034,746 discloses a system, method, andcomputer readable medium for inserting additional data, such ascommercials, into a digital audio/visual data stream. That system,however, is designed for inserting additional data having attributesdifferent from those of the primary data stream. As such, the system iscomplex and requires the decoder/receiver to be reinitialized with theattributes of the primary data stream after the additional data streamis played.

SUMMARY OF THE INVENTION

What is needed is a way to add a data effect such as a sound effect orsound bite to a compressed digital audio soundtrack without complexmixing, reinitialization, degradation of sound quality, loss ofsynchronization between the audio and video signals, or multipleconnections between equipment.

The present invention provides an apparatus and method for generating adata signal using a digitally encoded (or formatted), framed datastream. The method includes receiving a signal to insert a data effectinto the data stream, retrieving a data effect having the same format asthat of the data stream, detecting a first data stream frame boundary,inserting the data effect into the data stream at the first data streamframe boundary, detecting a second data stream frame boundary, andresuming the data stream at the second data stream frame boundary. Ifthe data stream can be of more than one format, the format of the datastream can first be determined. The data stream may be an audio streamformatted in MPEG format (including MPEG-1, MPEG-2, MP3, MPEG-4 and anylater versions), AC-3 format (including 2-channel, 5.1-channel,7.1-channel, and any later versions, and including Dolby® Digital AC-3and Dolby® Digital Surround AC-3), or DTS format.

Another method of the present invention for generating a video signalincludes receiving a signal to insert an audio effect into a digitalaudio stream, retrieving an audio effect having the same format as thatof the audio stream, retrieving a video effect corresponding to theaudio effect, inserting the audio effect into the audio stream at afirst audio stream frame boundary, inserting the video effect into avideo stream associated with the audio stream, and resuming the videostream and audio stream at a second audio stream frame boundary. Theaudio stream may be encoded in AC-3, MPEG, or DTS format.

A further method of the present invention maintains the synchronizationbetween a video stream and an associated encoded and framed digitalaudio stream. The method inserts into the audio stream at a first audiostream frame boundary an audio effect having the format of the audiostream, disposes of frames displaced by the audio effect, and resumesthe audio stream at a second audio stream frame boundary. As before, theaudio stream may be encoded in AC-3, MPEG, or DTS format.

The apparatus of the present invention includes a multiplexor and aprocessor. The multiplexor is used for inserting the data effect intothe data stream. The processor is used for detecting data stream frameboundaries, retrieving from a memory a data effect having the format ofthe data stream, and transmitting the formatted data effect to themultiplexor. If the data stream can be of more than one format, theprocessor can determine the format of the data stream. The data effectsmay be stored in a plurality of formats.

By having pre-formatted data effects already stored in a memory, thepresent invention generates a data signal including a data effect, suchas an audio effect, which is switched into a currently streaming,framed, encoded, digital data stream without decoding the digital datastream. More than one data effect can be switched into a single digitaldata stream. Detecting frame boundaries and switching the data effect inon those boundaries prevents annoying artifacts, such as pops in anaudio stream, from affecting the data stream. Because the pre-storedeffects have the same format as the data stream, no reinitialization isrequired as in the prior art. The present invention maintains thesynchronization between the video and audio streams by dropping framesthat are replaced by the data effect. The present invention also allowspre-stored video effects corresponding to the audio effects to bebroadcast in the video stream, synchronized with the audio effect.

Additional advantages of the invention will be set forth in thedescription which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. Theadvantages of the invention may be realized and obtained by means of theinstrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, in which like reference numerals representlike parts, are incorporated in and constitute a part of thespecification. The drawings illustrate presently preferred embodimentsof the invention and, together with the general description given aboveand the detailed description given below, serve to explain theprinciples of the invention.

FIG. 1 is a block diagram showing an embodiment of the presentinvention;

FIG. 2 is a block diagram of a set-top box in accordance with anembodiment of the present invention;

FIG. 3 is a block diagram of an effect switcher that inserts an audioeffect in accordance with an embodiment of the present invention;

FIG. 4 is a flowchart illustrating the steps for inserting an audioeffect in accordance with an embodiment of the present invention; and

FIGS. 5A and 5B illustrate a data stream before and after an audioeffect has been inserted in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

The present invention switches into an encoded (or formatted), frameddata stream a data effect with a format that matches the format of thedata stream. The invention allows the data effect to be switched inwithout decoding the data stream and mixing the data stream and the dataeffect.

The description of the drawings uses a cable television arrangementincluding a set-top box (STB) and an external audio decoder toillustrate the present invention with respect to adding an audio effectto a digital audio stream. However, the invention is not limited toaudio streams or cable television. Rather, the invention only requires aprimary digital data stream, which may be audio, video, or other data,that is transmitted in frames or packets, and some type of secondarydata effect, such as an audio or video effect, to be switched in. Thedata effect may be of any length, although it is noted that excessivelylong data effects may have the effect of displacing the primary datastream. Cable television is used as an example, but the invention may beused with satellite television, movies in a cinema, or in any othervenue or medium broadcasting framed data streams.

FIG. 1 illustrates an arrangement 100 in which a cable headend 110broadcasts or transmits a digital data stream, such as a movie, to acustomer's set-top box 120. The movie can be made up of an audio streamand a video stream. The video stream may be encoded, for example, in anMPEG format, which includes any of the current or future MPEG or digitalvideo formats. Other digital formats known in the art, such asQuicktime®, MJPEG, ASF (Advanced Streaming Format), and AVI (Audio VideoInterleaved), may be used. The audio stream may be encoded in AC-3format or some other suitable digital format such as DTS®, DTS-ES(Extended Surround), Dolby® Digital-Surround EX, DSD® (Direct StreamDigital), or the MPEG Audio layers. “AC-3 format” includes Dolby®Digital AC-3 format (2-channel) and Dolby® Surround Digital AC-3 format(5.1-channel and 7.1-channel). As noted above, the key property of thesedata streams is that they be digitally encoded/formatted and framed orpacketized.

In the illustrated embodiment, STB 120 separates the stream from thecable headend into audio and video streams and then decodes the MPEGvideo stream and outputs it as video for display. As shown in moredetail in FIG. 2, STB 120 typically includes a transport processor 210,memory 220, a digital video decoder 230, a graphics engine 240, acompositor 250, and an SPDIF (Sony/Philips Digital Interface) outputgenerator 260. In one embodiment, a single Broadcom 7020 high-definitionvideo graphics subsystem chip may be used, which includes the transportprocessor, the digital video decoder, the graphics engine, thecompositor, and the SPDIF generator, among other components. Transportprocessor 210 receives the movie stream from cable headend 110 andseparates the stream into digital audio and video streams. The digitalvideo stream (e.g., MPEG) is transmitted to digital video decoder 230which decodes the stream into analog video. Graphics engine 240generates display graphics (which may be stored in memory 220), andtransmits that signal to compositor 250 for mixing with the video andtransmission to TV 140. In a conventional STB, the digital audio streamis transmitted from transport processor 210 to SPDIF generator 260 foroutput to and decoding by external decoder 130. In the presentinvention, as discussed below, effect switcher 200 is added to thedigital audio path.

Although STB 120 could include circuitry to decode the AC-3 audiostream, the STB normally does not include such capability. This decodingis generally performed by external decoder 130. External decoders, madeby a number of manufacturers including VideoLogic and Yamaha, may bededicated and equipped with speakers and an amplifier or may be part ofa home theatre system that includes an audio/video receiver andpreamplifier with the appropriate format (e.g., AC-3) decoder. Afterexternal decoder 130 decodes the AC-3 audio stream, the decoded audiostream is transmitted to speakers 150 (which may be part of externaldecoder 130, a home theatre system, or TV 140) for broadcast.

Effect switcher 200, as shown in FIG. 2, which performs most of thesteps of the present invention, is included as a component of STB 120.Other embodiments may include effect switcher 200 as a separatecomponent placed between STB 120 and external decoder 130 or as acomponent of external decoder 130.

Effect switcher 200 can include processor 310 and multiplexor 320.Processor 310 can be any processor, such as a microprocessor or digitalsignal processor (DSP), capable of outputting control signals, acting ondigital data, and interacting with a memory, such as Intel® Pentiumprocessors, MIPS processors, Motorola® Power PC processors, or AnalogDevices® SHARC processors, for example. Memory 220 is shown in FIG. 2 asan input to processor 310 and is pictured as a hard disk drive, forexample, but can be any type of memory, including RAM. Multiplexor 320minimally must be able to multiplex the incoming digital data streamwith a data effect at the bit level, and can be implemented in softwareor programmable logic or as an ASIC (application specific integratedcircuit).

FIG. 4 is a flowchart describing the operation of effect switcher 200.After transport processor 210 receives a digitally encoded and framedaudio and video stream from cable headend 110, the transport processorsplits the stream into audio and video streams. The video stream (inMPEG format, for example) is decoded and transmitted to TV 140. Theaudio stream (in AC-3 format, for example) is transmitted to effectswitcher 200. In step 405, processor 310 looks at the stream headers todetect the format of the primary audio stream received from transportprocessor 210. As mentioned before, this format could be 2-channel,5.1-channel, or 7.1-channel AC-3, MPEG (or MP3), or other digital audioformat. In step 410, processor 310 receives a signal to insert an audioeffect into the audio stream. This signal can come, for example, from ane-mail or Internet browser application running on the STB platform, fromthe cable broadcaster sending an important message to the viewer, orfrom an interactive program guide running on the STB platform. Examplesof audio effects are a short “beep” or a “bong” sound (such as occurswith Microsoft Outlook or Lotus Notes) or a longer sound bite such as“You've Got Mail” (such as occurs with America Online) indicating anewly arrived e-mail message, a short sound indicating that somethird-party information (such as a weather advisory) is appearing on thetelevision screen, a short sound indicating that a user's entry on aremote keypad, for example, has been received by the STB, a longermessage from a stock ticker indicating a favorite stock has hit aspecified target price, etc., a tone indicating that the front door bellis ringing, and a ring indicating a telephone call from an expectedcaller (using Caller ID). The flowchart in FIG. 4 reflects that theformat does not change very often (e.g., once at the beginning of eachmovie). However, if the audio encoding format is less consistent andsubject to frequent change, requiring processor 310 to determine theformat “on the fly,” steps 405 and 410 could be interchanged.

In step 415, processor 310 retrieves from memory 220 the audio effectindicated by the insertion signal and having the correct format asdetected by the processor. Thus, memory 220 must have pre-stored anumber of different sound effects (e.g., beep, bong, “you've got mail,”“stock alert,” etc.) in each of the different formats in which a movieor program could be broadcast. In step 420, processor 310 transmits tomultiplexor 320 over data line 345 the appropriate sound effect and, instep 425, monitors the primary audio stream for the next frame boundary.Once the frame boundary is detected, processor 310 transmits overcontrol line 335 a control signal to multiplexor 320 to insert the audioeffect into the primary audio stream. In step 430, multiplexor 320inserts the audio effect into the primary audio stream. When the audioeffect is finished, in step 435 processor 310 monitors the primary audiostream for the next frame boundary, and, when the next frame boundary isdetected, notifies multiplexor 320 to resume transmitting in step 440the primary audio stream. The flowchart then loops back to step 410 towait for the next insertion signal so as to add more audio effects tothe audio stream.

Some of the other steps shown in FIG. 4 and described above may beperformed in other than the exact order shown. For instance, dependingon the timing between processor 310 and multiplexor 320, the audioeffect does not have to be transmitted to multiplexor 320 before theframe boundary is detected, as shown in steps 420 and 425. Instead,after retrieving the audio effect from memory 220 in step 415, processor310 detects the next frame boundary and, when found, transmits the audioeffect over data line 345 to multiplexor 320 at the same time theprocessor transmits the control signal over control line 335 tomultiplexor 320.

It should be noted that in order to maintain the synchronization betweenthe primary audio stream and the associated video stream, the audioeffect frames actually replace the audio stream frames that wereoriginally transmitted by the STB. Thus, while the audio effect is beinginserted into the primary audio stream, the replaced audio stream framesare disposed of (or “dropped”) by processor 310. This process isdepicted in FIGS. 5A and 5B. FIG. 5A is a schematic of the primary audiostream which is made up of many audio frames 501, 502, . . . , 509.(Note that reference numeral 505 indicates a plurality of audio frames.)FIG. 5B is a schematic of the modified audio stream with the audioeffect, made up of frames 521–523, inserted between frames 503 and 507(again, note that reference numeral 522 indicates a plurality of audioframes). The streams in both FIGURES are synchronized with the videostream because frames 504–506 have been dropped. Generally, the videostream has already been decoded into analog video and may or may notcontain graphics.

The present invention can be used to indicate other types of audioeffects, such as in home networking applications where the user sets analarm or indicator, e.g., oven timer, alarm clock/reminder, or wants tohear the door bell, door alarm, fire/burglar alarm, baby monitor, andsignals from other appliances in the home—even a PC—and wants to hearthe audible while listening to audio on a home theater.

In addition, the present invention can be used to generate a videoeffect that correlates with an audible signal. For instance, apre-stored, pre-formatted video effect, such as an icon or characters,can be displayed on the TV screen if the effect switcher receives aneffect insertion signal from one of the applications running on the STB.Thus, if the audible signal is receipt of e-mail, an icon of a mailboxcould flash on the TV screen. Similarly, if the audible signal isgenerated by a baby monitor, an icon of a baby crying could flash on theTV screen. Other audio effect/video icon pairs could be used, such asoven timer/alarm clock icon, door bell/open door icon, fire alarm/firetruck icon, etc. Alphanumeric characters could be displayed along withor instead of an icon. Such an icon or characters can be generated byhaving the effect switcher send a signal to graphics engine 240 oncontrol line 355 to fetch from the memory a pre-stored, analog videoicon or character display, which is transmitted to compositor 250 todisplay on TV 140 at the same time the corresponding audio effect isbroadcast on speakers 150.

As discussed above, additional advantages and modifications will readilyoccur to those skilled in the art. Therefore, the present invention inits broader aspects is not limited to the specific embodiments, details,and representative devices shown and described herein. Accordingly,various changes, substitutions, and alterations may be made to suchembodiments without departing from the spirit or scope of the generalinventive concept as defined by the appended claims.

1. A method for generating a data signal using an encoded and framed digital data stream, the method comprising: receiving a signal to insert a data effect into the data stream; identifying, from a number of different data effects, one that has a format of the data stream; retrieving the data effect having the format of the data stream; detecting a first data stream frame boundary; inserting the data effect into the data stream at the first data stream frame boundary; detecting a second data stream frame boundary; and resuming the data stream at the second data stream frame boundary.
 2. The method according to claim 1, further comprising determining the format of the data stream, wherein the retrieved data effect has the same format as that of the data stream.
 3. The method according to claim 1, wherein the data stream is an audio stream.
 4. The method according to claim 3, wherein the data effect is an audio effect.
 5. The method according to claim 4, wherein the audio stream is encoded in AC-3 format.
 6. The method according to claim 5, wherein the audio stream is encoded in 2-channel AC-3 format.
 7. The method according to claim 5, wherein the audio stream is encoded in 5.1-channel AC-3 format.
 8. The method according to claim 5, wherein the audio stream is encoded in 7.1-channel AC-3 format.
 9. The method according to claim 4, wherein the audio stream is encoded in MPEG format.
 10. The method according to claim 4, wherein the audio stream is encoded in DTS format.
 11. A method for generating an audio signal using an encoded and framed digital audio stream, the method comprising: detecting a first audio stream frame boundary; identifying, from a number of different pre-stored audio effects, one that has a format of the audio stream; inserting into the audio stream at the first audio stream frame boundary the pre-stored audio effect having the format of the audio stream; detecting a second audio stream frame boundary; and resuming the audio stream at the second audio stream frame boundary.
 12. The method according to claim 11, further comprising determining the format of the audio stream, wherein the pre-stored audio effect has the same format as that of the audio stream.
 13. The method according to claim 11, wherein the audio stream is encoded in AC-3 format.
 14. The method according to claim 13, wherein the audio stream is encoded in 2-channel AC-3 format.
 15. The method according to claim 13, wherein the audio stream is encoded in 5.1-channel AC-3 format.
 16. The method according to claim 13, wherein the audio stream is encoded in 7.1-channel AC-3 format.
 17. The method according to claim 11, wherein the audio stream is encoded in MPEG format.
 18. The method according to claim 11, wherein the audio stream is encoded in DTS format.
 19. A method for generating a video signal, the method comprising: receiving a signal to insert an audio effect into an encoded and framed digital audio stream; identifying, from a number of different audio effects, one that has a format of the audio stream retrieving the audio effect having the format of the audio stream; retrieving a video effect corresponding to the audio effect; inserting the audio effect into the audio stream at a first audio stream frame boundary; inserting the video effect into a video stream associated with the audio stream; and resuming the video stream and the audio stream at a second audio stream frame boundary.
 20. The method according to claim 19, further comprising determining the format of the audio stream, wherein the retrieved audio effect has the same format as that of the audio stream.
 21. The method according to claim 19, wherein the audio stream is encoded in AC-3 format.
 22. The method according to claim 19, wherein the audio stream is encoded in MPEG format.
 23. The method according to claim 19, wherein the audio stream is encoded in DTS format.
 24. A method for maintaining synchronization between a video stream and an associated encoded and framed digital audio stream, the method comprising: inserting into the audio stream at a first audio stream frame boundary an audio effect having the format of the audio stream; disposing of frames displaced by the audio effect; and resuming the audio stream at a second audio stream frame boundary.
 25. The method according to claim 24, wherein the audio stream is encoded in AC-3 format.
 26. The method according to claim 24, wherein the audio stream is encoded in MPEG format.
 27. The method according to claim 24, wherein the audio stream is encoded in DTS format.
 28. An apparatus for generating a data signal using an encoded and framed digital data stream, the apparatus comprising: a multiplexor for inserting a data effect into the data stream; and a processor for detecting frame boundaries in the data stream between which the data effect is inserted, for identifying, from a number of different data effects, one that has a format of the data stream, for retrieving from a memory the data effect having the format of the data stream, and for transmitting the formatted data effect to the multiplexor.
 29. The apparatus according to claim 28, wherein the processor determines the format of the data stream.
 30. The apparatus according to claim 28, wherein the data effects are stored in a plurality of formats.
 31. The apparatus according to claim 28, wherein the data stream is an audio stream.
 32. The apparatus according to claim 31, wherein the data effect is an audio effect.
 33. The apparatus according to claim 32, wherein the audio stream is encoded in AC-3 format.
 34. The apparatus according to claim 33, wherein the audio stream is encoded in 2-channel AC-3 format.
 35. The apparatus according to claim 33, wherein the audio stream is encoded in 5.1-channel AC-3 format.
 36. The apparatus according to claim 33, wherein the audio stream is encoded in 7.1-channel AC-3 format.
 37. The apparatus according to claim 32, wherein the audio stream is encoded in MPEG format.
 38. The apparatus according to claim 32, wherein the audio stream is encoded in DTS format.
 39. A method for generating a data signal using an encoded and framed digital data stream, the method comprising: receiving a signal to insert a data effect into the data stream; retrieving, the data effect having the format of the data stream; detecting a first data stream frame boundary; inserting the data effect into the data stream at the first data stream frame boundary; detecting a second data stream frame boundary; disposing of frames displaced by the data effect; and resuming the data stream at the second data stream frame boundary.
 40. A method for generating an audio signal using an encoded and framed digital audio stream, the method comprising: detecting a first audio stream frame boundary; inserting into the audio stream at the first audio stream frame boundary the pre-stored audio effect having the format of the audio stream; detecting a second audio stream frame boundary; disposing of frames displaced by the audio effect; and resuming the audio stream at the second audio stream frame boundary.
 41. A method for generating a video signal, the method comprising: receiving a signal to insert an audio effect into an encoded and framed digital audio stream; retrieving the audio effect having the format of the audio stream; retrieving a video effect corresponding to the audio effect; inserting the audio effect into the audio stream at a first audio stream frame boundary; inserting the video effect into a video stream associated with the audio stream; disposing of frames displaced by the audio effect; and resuming the video stream and the audio stream at a second audio stream frame boundary.
 42. An apparatus for generating a data signal using an encoded and framed digital data stream, the apparatus comprising: a multiplexor for inserting a data effect into the data stream; and a processor for detecting frame boundaries in the data stream between which the data effect is inserted, for retrieving from a memory the data effect having the format of the data stream, for disposing of frames displaced by the data effect, and for transmitting the formatted data effect to the multiplexor. 